This invention relates to modified olefin polymerization catalyst supports.
Silica supported chromium oxide catalysts can be used to prepare olefin polymers in a hydrocarbon solution to give a product having excellent characteristics from many standpoints. Molecular weight can be controlled in such processes simply by adjusting the temperature. Supported chromium oxide catalysts can also be used to prepare olefin polymers in a slurry system wherein the polymer is produced in the form of small particles of solid material suspended in the diluent. This process, frequently referred to as a particle-form process, has the advantage of being less complex, but does not produce polymers which are exactly comparable to solution polymers i.e. in molecular weight distribution, for example. In addition, there is an inherent limitation on control of molecular weight through temperature adjustment since excessive increase in the temperature to effect lower molecular weight (higher melt index) polymer causes the polymer to go into solution and thus destroys the particle-form process.